Preheat the oven. Preheat the oven to 375°F. Grease a 12-cup muffin pan or line with muffin liners.
Combine the wet ingredients. In a large bowl, whisk together the applesauce, Greek yogurt, eggs, melted butter, maple syrup, and vanilla until well combined.
Soften the oats. Stir in the rolled oats and let the mixture sit for 5–10 minutes. This gives the oats time to soften and absorb some of the moisture.
Add the dry ingredients. Add the flour, cinnamon, baking powder, baking soda, and salt. Gently stir just until combined. Be careful not to overmix. Stir in raisins if using.
Bake. Divide the batter evenly among the 12 muffin cups. Bake for 17–20 minutes, or until the muffins are lightly golden and a toothpick inserted into the center comes out clean.
Cool. Let the muffins cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
Keep cooled muffins in an airtight container at room temperature for up to 2 days, or in the refrigerator for up to 5 days.